Methods of production for corrosion-resistant bit patterned media (bpm) and discrete track media (dtm)

ABSTRACT

A method for producing a magnetic recording medium in one embodiment includes forming a magnetic material layer above a substrate, transferring an uneven pattern to the magnetic material layer to form concave portions and convex portions, the convex portions being magnetic regions, depositing a nonmagnetic material above the concave portions to form nonmagnetic regions, forming an oxide layer and/or hydroxide layer above the magnetic regions of the recording layer, and forming an organic material layer which exhibits a corrosion-inhibiting characteristic with respect to cobalt or cobalt alloy above the oxide layer and/or hydroxide layer.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/466,970 filed May 8, 2012, which is herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to discrete track and bit patterned media,and more particularly, this invention relates to discrete track and bitpatterned media having reduced corrosion and controlling corrosion inproducing discrete track and bit patterned media.

BACKGROUND

The development of discrete track media (DTM), in which adjacentrecording tracks are separated by a groove or nonmagnetic body in orderto suppress magnetic interference between tracks, and bit patternedmedia (BPM), in which adjacent recording bits are separated by a grooveor nonmagnetic body in order to suppress magnetic interference betweenbits, has allowed for the realization of high density recording, wherethese technologies aid in the control of magnetic interference betweenadjacent magnetic data storage areas (tracks or bits).

There has been strong demand in recent years for greater volume inmagnetic recording devices and for higher recording density, not only indomestic electronic appliances such as personal computers, but alsoother devices equipped with compact, large-capacity magnetic disk(s). Inorder to respond to this demand, there has been great effort put intodeveloping magnetic heads and magnetic recording media. An increasedareal recording density is desired for these devices, and efforts arebeing made to reduce the scale and to achieve even more dramaticincreases in recording density.

Surface planarity is important in magnetic recording media in order tomaintain flying stability of the magnetic head. Surface planarity isespecially important in the case of DTM and BPM in which the arealrecording density is high and the recording domain is small, such thatthe grooves between magnetic regions are filled by nonmagnetic material.In addition, with DTM and BPM, a protective film made of a carbon-basedmaterial is generally formed on the recording layer in order to protectthe recording layer and to absorb lubricant, in the same way as withconventional recording media. Among carbon-based materials that may beused for the nonmagnetic material, one preferred material isdiamond-like-carbon (DLC), which is amorphous, and therefore hasexcellent surface planarity, durability, and corrosion resistance.

Meanwhile, improvements in the reliability of DTM and BPM have broughtto light the problems of corrosion caused by damage when the magneticfilm is rendered uneven through dry etching or the like, and corrosioncaused by extremely small defects and gaps between the magnetic regionand nonmagnetic region of the recording layer. One example of aconventional technology for improving corrosion resistance involves asoft magnetic underlayer which is the primary cause of corrosion inperpendicular magnetic recording media. The corrosion resistance isimproved by selecting a particularly resistant combination of thestructure and material of the seed layer, which is the layer above thesoft magnetic underlayer. In addition, there is another conventionalmethod to inhibit corrosion of the magnetic region in DTM and BPM byforming a conductive film between the recording layer and the protectivefilm.

However, if a protective film is formed as the layer above the magneticregion in order to inhibit corrosion thereof, the magnetic distancebetween the magnetic head and the magnetic recording medium increasesand the magnetic recording characteristics deteriorate. On the otherhand, if the protective film is made thinner in order to improve themagnetic characteristics, it is difficult to achieve results whichsatisfy the product performance from the point of view of corrosionresistance. Accordingly, with conventional technologies of preventingcorrosion of the magnetic region of the magnetic recording layer, thereare problems, such as problems in achieving both high magnetic recordingcharacteristics and corrosion resistance at the same time.

SUMMARY

In one embodiment, a method for producing a magnetic recording mediumincludes forming a magnetic material layer above a substrate,transferring an uneven pattern to the magnetic material layer to formconcave portions and convex portions, the convex portions being magneticregions, depositing a nonmagnetic material above the concave portions toform nonmagnetic regions, forming an oxide layer and/or hydroxide layerabove the magnetic regions of the recording layer, and forming anorganic material layer which exhibits a corrosion-inhibitingcharacteristic with respect to cobalt or cobalt alloy above the oxidelayer and/or hydroxide layer.

Any of these embodiments may be implemented in a magnetic data storagesystem such as a disk drive system, which may include a magnetic head, adrive mechanism for passing a magnetic storage medium (e.g., hard disk)over the head, and a control unit electrically coupled to the head forcontrolling operation of the head.

Other aspects and advantages of the present invention will becomeapparent from the following detailed description, which, when taken inconjunction with the drawings, illustrate by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified drawing of a magnetic recording disk drivesystem.

FIG. 2A is a schematic representation in section of a recording mediumutilizing a longitudinal recording format.

FIG. 2B is a schematic representation of a conventional magneticrecording head and recording medium combination for longitudinalrecording as in FIG. 2A.

FIG. 2C is a magnetic recording medium utilizing a perpendicularrecording format.

FIG. 2D is a schematic representation of a recording head and recordingmedium combination for perpendicular recording on one side.

FIG. 2E is a schematic representation of a recording apparatus adaptedfor recording separately on both sides of the medium.

FIG. 3A is a cross-sectional view of one particular embodiment of aperpendicular magnetic head with helical coils.

FIG. 3B is a cross-sectional view of one particular embodiment of apiggyback magnetic head with helical coils.

FIG. 4A is a cross-sectional view of one particular embodiment of aperpendicular magnetic head with looped coils.

FIG. 4B is a cross-sectional view of one particular embodiment of apiggyback magnetic head with looped coils.

FIGS. 5A-5B schematically show cross-sectional structures of a magneticrecording medium according to an exemplary embodiment.

FIGS. 6A-6L show steps in a method for producing a magnetic recordingmedium according to an exemplary embodiment.

FIGS. 7A-7B schematically show a cross-sectional structure of a magneticrecording medium according to an exemplary embodiment.

FIGS. 8A-8K show steps in a method for producing a magnetic recordingmedium according to an exemplary embodiment.

FIG. 9 is a schematic view from above of a magnetic recording deviceaccording to an exemplary embodiment.

FIG. 10 is a cross-sectional view of a magnetic recording deviceaccording to an exemplary embodiment.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

It must also be noted that, as used in the specification and theappended claims, the singular forms “a,” “an,” and “the” include pluralreferents unless otherwise specified.

In one general embodiment, a magnetic recording medium includes amagnetic recording layer including a magnetic material characterized byhaving convex and concave portions, the convex portions acting asmagnetic regions, a nonmagnetic material positioned within each concaveportion of the magnetic material which act as nonmagnetic regions thatseparate the magnetic regions, an organic material layer which exhibitsa corrosion-inhibiting characteristic with respect to cobalt or cobaltalloy positioned on a nonmagnetic region side of each concave portion,and an oxide layer and/or hydroxide layer positioned adjacent theorganic material layer on a magnetic region side of each concave portionof the magnetic material.

In another general embodiment, a magnetic recording medium includes apatterned recording layer, a protective film positioned above thepatterned recording layer, an oxide layer and/or hydroxide layerpositioned above a magnetic layer side of the patterned recording layerpositioned at least in defect portions of the protective film, and anorganic material layer which has a corrosion-inhibiting characteristicwith respect to cobalt or cobalt alloy positioned above and in contactwith an upper surface of the oxide layer and/or hydroxide layer.

In yet another general embodiment, a method for producing a magneticrecording medium includes forming a magnetic material layer above asubstrate, transferring an uneven pattern to the magnetic material layerto form concave portions and convex portions, the convex portions beingmagnetic regions, depositing a nonmagnetic material above the concaveportions to form nonmagnetic regions, forming an oxide layer and/orhydroxide layer above the magnetic regions of the recording layer, andforming an organic material layer which exhibits a corrosion-inhibitingcharacteristic with respect to cobalt or cobalt alloy above the oxidelayer and/or hydroxide layer.

According to one embodiment, a discrete track medium (DTM) or a bitpatterned medium (BPM), achieves excellent magnetic recordingcharacteristics and corrosion resistance by having a corrosion-resistantlayer at an interface of a magnetic region and a filler region of themagnetic recording layer, and by selecting a combination of thestructure and material thereof.

In order to achieve the desired DTM or BPM having excellent corrosionresistance, a DTM or BPM includes a magnetic recording layer formedusing an uneven pattern above a substrate, in which a magnetic region isformed on convex portions of the uneven pattern and a filler region isburied in concave portions of the uneven pattern. In addition, a layerincluding an organic material which exhibits a corrosion-inhibitingcharacteristic, such as cobalt or a cobalt alloy, and an oxide layerand/or hydroxide layer are formed at an interface of the magnetic regionand the filler region. It has been found that the oxide layer and/orhydroxide layer is/are effective for stably holding a silane couplingagent on the metal surface of the magnetic region.

Cobalt and cobalt alloys not only have poor corrosion resistance, theyalso has very low potential in an aqueous solution environment, andtherefore galvanic corrosion occurs readily between adjacent metals. Inthe case of a granular magnetic recording layer, Ru or a Ru alloy may beformed in a layer under the recording layer in order to promotesegregation of the oxide at the crystal grain boundary in the recordinglayer. The Ru or Ru alloy has very high potential as it is a noblemetal, so when areas of the concave portions which comprise theprocessed parts of the recording layer come into contact with the Ru orRu alloy due to processing damage, galvanic corrosion of the Co alloy inthe recording layer occurs, and this effect is more rapid than simplecorrosion. Furthermore, in DTM and BPM, damage occurs when the magneticfilm is rendered uneven, such as through dry etching or the like, andtherefore there is a clear problem in that corrosion is accelerated atthe interface of the magnetic region.

In view of this, a layer comprising an organic material which exhibits acorrosion-inhibiting characteristic with respect to cobalt or a cobaltalloy, and an oxide layer and/or hydroxide layer may be formed in themagnetic region of the processed part in the recording layer, in orderto inhibit corrosion of the magnetic region, which comprises theprocessed part of the recording layer. Here, the characteristics of theorganic material selected may include, from a corrosion point ofview, 1) exhibiting a corrosion-inhibiting characteristic with respectto Co or a Co alloy; 2) comprising a film which has as few defects aspossible, resulting in a smooth and accurate surface; and 3) having astructure which does not produce deterioration in the magnetic recordingcharacteristics due to increased magnetic distance between the magnetichead and the magnetic recording medium, such as by being capable ofbeing thin.

The corrosive environment is essentially an aqueous environment, butother factors include oxidation or alkalization brought about bylubricant decomposition, and contamination by chlorides, and thereforecorrosion resistance covering a wide pH environment is preferred.However, the location where corrosion is a particular problem is at theinterface between the magnetic region or layer and the nonmagneticregion or layer in the recording layer, and voids are believed to formin this region, so the environment is acidic when corrosion occurs inthis area. With this assumption, it can be further assumed thatcorrosion resistance is particularly useful in the acidic region.

Regarding a corrosion-inhibiting characteristic with respect to Co or aCo alloy, as a result of various investigations, it was found that it ispossible to inhibit Co or Co alloy corrosion by forming a heterocyclicorganic compound layer, such as benzotriazole (BTA). It is believed thatthe corrosion resistance is improved because the heteroatoms in theheterocycles and cobalt in the recording layer are strongly bonded, andthe BTA forms a network, in one approach.

Regarding a film which has as few defects as possible, in the case of aheterocyclic compound layer such as BTA, a thin film of Co oxide (suchas a layer as thin as a few atoms) is invariably spontaneously formed onthe surface of the Co or Co alloy, but BTA molecules form strongcoordinate bonds with Co oxide, and BTA molecules also form covalentbonds between themselves, so a strong BTA polymer film is formed at thesurface of the Co or Co alloy, and therefore an extremely refined filmhaving excellent adhesion and no defects may be formed, in one approach.

Regarding a structure which does not produce deterioration in themagnetic recording characteristics due to increased magnetic distancebetween the magnetic head and the magnetic recording medium, achemically passive metal or alloy thereof, or a carbon layer may beprovided in a planar direction of the recording layer during theproduction process (in the region which is read/written by the head), aswill be described later, after which it may be removed. This allows forthe above problem to be resolved. Even if the film were to remain, aheterocyclic compound such as BTA may be used in the manner describedabove, and the film would be almost a single-molecule film, so it wouldbe very thin and would not give rise to a deterioration in the magneticrecording characteristics.

In addition, in some approaches, regarding the organic material layer,the organic material film may be stably formed on the magnetic layer,and the magnetic layer may be unaffected by the formation of the organicmaterial film.

Regarding stably forming the organic material film on the magneticlayer, it was found that the organic material layer is stably formed onan oxide film having a greater thickness than the spontaneous oxide filmthickness. That is to say, for the oxide film and/or hydroxide filmdescribed herein, a layer comprising an organic material which exhibitsa corrosion-inhibiting characteristic with respect to cobalt or cobaltalloy may be formed above or directly on the magnetic film. The magneticfilm is metal, so a spontaneous oxide film is typically formed.

The thickness of this film is on the order of several tenths of ananometer, but this thickness may be inadequate as being too thin, andbetter results may be obtained from a film having a thickness of atleast 1.0 nm. Because of this, an oxidant may also be present and anoxide and/or hydroxide layer formed when the organic material layer isformed may be used, or an oxide and/or hydroxide layer may be formedbefore the organic material layer is formed.

Regarding the magnetic layer being unaffected by the formation of theorganic material film, suitably selecting conditions under which theoxide film is formed may provide this result.

Consequently, corrosion resistance may be improved in a DTM and/or a BPMby forming a layer comprising an organic material which exhibits acorrosion-inhibiting characteristic with respect to cobalt or cobaltalloy, and an oxide layer and/or a hydroxide layer at the interface ofthe magnetic region and the filler region in the magnetic recordinglayer.

Now referring to FIG. 5A, a cross-sectional view of a structure of amagnetic disk 1 in a basic patterned medium is shown according to oneembodiment. A glass disk substrate 11 may be used for the substrate, orany other suitable substrate material known in the art. The magneticdisk 1 also comprises, according to one embodiment, an adhesion layer12, a soft magnetic underlayer 13, a seed layer 14, an interlayer 15,and a recording layer 16 which are formed above the substrate 11. Therecording layer 16 is formed with an uneven upper surface which providesthe recording layer 16 with unevenness, with convex portions formingmagnetic regions 17, and concave portions after being filled with anonmagnetic material, forming nonmagnetic regions 18. A protective filmB layer 25 may be formed at a bottom of the concave portions.

As shown in FIG. 5B, which is a detailed view of an interface betweenthe magnetic region 17 and the nonmagnetic region 18 as shown in FIG.5A, layer 19 comprises an organic material layer 19 a which exhibits acorrosion-inhibiting characteristic with respect to cobalt or cobaltalloy, and an oxide and/or hydroxide layer 19 b, which is formed on aninterior of the organic material layer 19 a with respect to therecording layer 16 concave portions. The organic material layer 19 a andthe oxide and/or hydroxide layer 19 b may be formed at an interfacebetween the magnetic region 17 and the nonmagnetic region 18.

Referring again to FIG. 5A, according to one embodiment, a protectivefilm A 20 may be formed above or directly on the recording layer 16.Also, in some approaches, a lubricant (not shown) may be coated on therecording layer 16.

There is no particular limitation as to the material which may be usedfor the adhesion layer 12 provided that it exhibits excellent adhesionto the substrate 11 and surface planarity, but it may preferably be analloy comprising at least two metals chosen from Ni, Al, Ti, Ta, Cr, Zr,Co, Hf, Si, and B. More specifically, NiTa, AlTi, AlTa, CrTi, CoTi,NiTaZr, NiCrZr, CrTiAl, CrTiTa, CoTiNi, or CoTiAl may be used, amongother possibilities known in the art.

There is no particular limitation as to the material of the softmagnetic underlayer 13 provided that saturation magnetic flux density(Bs) of this layer is at least about 1.0 Tesla, uniaxial anisotropy isimparted in the radial direction of the disk substrate 11, coerciveforce measured in the head travel direction is no greater than 1.6k/A/m, and surface planarity is excellent. Specifically, theabovementioned characteristics are readily achieved if an amorphousalloy is used, such as one comprising Co, Ni, or Fe as a main component(50 at % or greater), to which Ta, Hf, Nb, Zr, Si, B, C or the like isadded. In addition, it is possible to reduce the noise by adopting alaminated structure in which a nonmagnetic layer is inserted into thesoft magnetic underlayer 13, in one approach. CoCr alloy, Ru, Cr or Cu,and MgO, etc., may preferably be used for this nonmagnetic layer.

The role of the seed layer 14 is to control the orientation and crystalgrain size of the interlayer 15, and it is possible to use an fcc alloycomprising Ni as a main component. Typical materials which may be usedinclude alloys comprising at least one element selected from W, Fe, Ta,Ti, Ta, Nb, Cr, Mo, V, Cu and the like, with Ni. Furthermore, in orderto improve the corrosion resistance, the seed layer 14 may have atwo-layer structure in which the abovementioned seed layer serves as arecording layer-side seed layer (second seed layer), and an alloy inwhich Ta, Ti, Nb, and/or Al is added to Cr is inserted between thesecond seed layer and the soft magnetic underlayer 13 as a first seedlayer. Ru alone, or an alloy having a hexagonal close-packed (hcp)structure or fcc structure comprising Ru as a main component may be usedas the interlayer 15. A CoCr alloy such as CoCrPt alloy, or an alloyhaving a granular structure comprising FePt alloy as a main component towhich an oxide, such as SiO₂ is added, specifically CoCrPt—SiO₂,CoCrPt—MgO, CoCrPt—TaO, or the like, may be used as the magnetic layermaterial 17 which is formed on the convex portions of the recordinglayer 16. Furthermore, an oxide such as SiO₂, Al₂O₃, TiO₂, ferrite, anitride such as AlN, and/or a carbide such as SiC, may be used as thenonmagnetic material 18 which is formed in the concave portions of therecording layer 16. For the Co and Pt concentrations, the Crconcentration may preferably be from about 15 at % to about 25 at %, andthe Cr concentration may preferably be from about 10 at % to about 20 at%. Of course, other ranges are also possible, as would be known to oneof skill in the art upon reading the present descriptions.

The protective film B 25 which is positioned at a bottom of the magneticmaterial 17 is a layer which is introduced with the aim of correctingdefects caused by damage sustained during the magnetic layer processing,if any (which there typically is), and it comprises a chemically passivemetal or alloy thereof, a carbon layer, or some other suitable material.Cr, Ti, Ni, Mo, Nb, W, Ta, Zr or an alloy comprising at least one ofthese may be used as the chemically passive metal, in some approaches.An alloy comprising Cr may be preferred in one approach.

The organic material layer 19 a which is positioned at the interface ofthe magnetic layer 17 and the nonmagnetic layer 18 should, in preferredembodiments, exhibit a corrosion-inhibiting characteristic with respectto cobalt or cobalt alloy. A heterocyclic compound such as BTA isespecially effective as the organic material layer, but is not solimited. Heterocyclic compounds are compounds comprising heterocycleswhich include heteroatoms which are preferably nitrogen atoms, sulfuratoms, oxygen atoms, selenium atoms, tellurium atoms, phosphorus atoms,boron atoms, etc., with nitrogen atoms, sulfur atoms, and oxygen atomsbeing most preferred. There is no limit to the number of heteroatomsincluded in the heterocyclic compound, but two or more heteroatomsproduces a strong anti-corrosion characteristic. Specific heterocyclesinclude benzotriazole rings, benzothiazole rings, benzimidazole rings,triazole rings, imidazole rings, pyridine rings, quinoline rings, etc.In addition to the above listed structures, there are also thiadiazolerings. However, this does not imply any limitation. Substituent groupsmay also be present, such as alkyl groups, sulfo groups, carboxylgroups, etc. Specifically, benzotriazole; 1,2,3-triazole;1,2,3,4-tetrazole; 3-amino-1,2,4-triazole; nitro-1H-benzotriazole;carboxy benzotriazole; 5-methyl-benzotriazole; uric acid, etc., may beused, but this does not imply any limitation to what may be used.

In one embodiment, a magnetic recording medium comprises a magneticrecording layer comprising a magnetic material characterized by havingconvex and concave portions, the convex portions acting as magneticregions, a nonmagnetic material positioned within each concave portionof the magnetic material which act as nonmagnetic regions that separatethe magnetic regions, an organic material layer which exhibits acorrosion-inhibiting characteristic with respect to cobalt or cobaltalloy positioned on a nonmagnetic region side of each concave portion,and an oxide layer and/or hydroxide layer positioned adjacent theorganic material layer on a magnetic region side of each concave portionof the magnetic material.

Furthermore, in one approach, the organic material layer and the oxidelayer and/or hydroxide layer may be only positioned on side walls ofeach concave portion of the magnetic material, or in an alternateapproach, on side walls and a bottom surface of each concave portion ofthe magnetic material.

In more approaches, the magnetic regions may be in contact with and/orbonded with the oxide layer and/or hydroxide layer, the medium mayfurther comprise an interlayer positioned below the recording layer, aseed layer positioned below the interlayer, and an adhesion layerpositioned below the seed layer, and/or the oxide layer and/or hydroxidelayer may have a thickness of at least about 1 nm.

In addition, any magnetic recording medium described herein may beincluded in a magnetic data storage system. The magnetic data storagesystem may include at least one magnetic head, a magnetic recordingmedium as described herein according to any of various embodiments, adrive mechanism for passing the magnetic medium over the at least onemagnetic head, and a controller electrically coupled to the at least onemagnetic head for controlling operation of the at least one magnetichead.

In another embodiment, a magnetic recording medium comprises a patternedrecording layer, a protective film positioned above the patternedrecording layer, an oxide layer and/or hydroxide layer positioned abovea magnetic layer side of the patterned recording layer positioned atleast in defect portions of the protective film, and an organic materiallayer which has a corrosion-inhibiting characteristic with respect tocobalt or cobalt alloy positioned above and in contact with an uppersurface of the oxide layer and/or hydroxide layer.

A method for forming the organic material layer 19 a using aheterocyclic compound, in one embodiment, may be carried out byimmersing the magnetic recording medium in an aqueous solution ororganic solvent including at least one of the abovementionedheterocycles for a predetermined time, or by spraying the same.Furthermore, a compound containing N or S and O which is notheterocyclic but has unpaired electrons having an attraction effect,such as amine, is also effective. As mentioned above, an oxide layerand/or hydroxide layer may be formed on the magnetic layer 17 in orderto form the organic material layer 19 a directly on the magnetic layer17, in one approach.

Immersing the disk in an aqueous solution having the organic material(wet method) is a suitable method for forming the organic material layer19 a, in one approach, and a method in which the disk is exposed on anorganic solid inside a sealed vessel is also effective as another method(dry method), according to one approach.

The method for forming the oxide layer and/or hydroxide layer 19 b onthe magnetic layer 17 may be a method in which an oxidant is alsopresent when the organic material layer 19 a is formed, or a methodinvolving heating in air. Oxidants which may be used include: hydrogenperoxide, chloric acid, perchloric acid, persulfuric acid, nitric acid,and salts thereof, and ceric ammonium nitrate, etc. When the treatmentis carried out by the wet method, it is also effective to add asurfactant in order to raise the permeability of the solution in oneapproach. Surfactants which may be used include: anionic surfactantssuch as dodecyl sulfate, stearic acid, and toluenesulfonate; cationicsurfactants such as cetyltrimethyl ammonium salt and tetramethylammoniumhydroxide; amphoteric surfactants such as lauryl betaine; and/ornon-ionic surfactants such as polyethylene glycol and polyvinyl alcohol.

The material used for the protective film A 20 which is formed on therecording layer 16 may comprise a hard carbon film, such asdiamond-like-carbon (DLC), for example. A lubrication layer may furtherbe positioned on the protective film 20, although this is not shown inFIG. 5A. Perfluoropolyether (PFPE) or a Fomblin-based lubricant may beused for the lubrication layer, in some approaches.

A method for producing the abovementioned magnetic recording medium isnow described with reference to FIGS. 6A-6L. The magnetic recordingmedium may be produced using a sputtering apparatus. In a firstoperation, as shown in FIG. 6A, a glass substrate of diameter 63.5 mmmay be used for the substrate 11. An adhesion layer 12, soft magneticunderlayer 13, seed layer 14, interlayer 15, and a recording layer(magnetic region) 17 may be formed in succession via sputtering or someother deposition technique. A composition and thickness of each layermay be as shown in Table 1, according to one exemplary embodiment. Thecompositions and thicknesses shown in Table 1 are merely examples, andthe same effects may still be achieved if other compositions andthicknesses are used, as would be understood by one of skill in the art.For example, the same effects may still be achieved if Cr₅₀Ti₅₀ is usedfor the first seed layer and Ni₉₀Ti₁₀ is used for the second seed layer.Also, if NiWTa is used for the seed layer 14, without having a doubleseed layer; or if CoCrPt—TaO is used in the recording layer 17.

TABLE 1 Target Film Composition Thickness (at %) (nm) Adhesion LayerNi₆₃Ta₃₇ 10 Soft First Soft Magnetic Layer Co₉₂Ta₃Zr₅ 50 Magnetic SecondSoft Magnetic Layer Ru 0.8 Underlayer Third Soft Magnetic Layer Ta₇₀Cr₃₀50 Seed First Seed Layer Ta₇₀Cr₃₀ 2 Layer Second Seed Layer Ni₉₂W₈ 5Interlayer Ru 16 Recording Layer CoCrPt—SiO₂ 16

Next, as shown in FIGS. 6B-6C according to one embodiment, a protectivefilm C 24 may be formed on the magnetic region 17 of the recordinglayer, after which a resist 21 may be coated on the protective film C,such as via spin-coating or some other suitable method. A positiveresist may be used as a material for the resist layer, for example. Theprotective film C 24 may be formed in order to prevent corrosion of therecording layer (magnetic region) 17 in the step of forming discretetracks by application of the resist 21.

Next, as shown in FIG. 6D according to one embodiment, an uneven patternhaving predetermined gaps corresponding to a servo pattern in a servoregion and a track pattern in a data region may be transferred to theresist layer, such as via a nanoimprint process using a transfer device22, or some other method. As shown in FIG. 6E according to oneembodiment, the protective layer C 24 in the resist removal part maythen be removed via reactive ion beam etching or some other method. Asshown in FIG. 6F, in one approach, part of the magnetic region 17 of therecording layer may be further removed using ion milling or some othermethod, in order to form the concave portions.

Here, as shown in FIG. 7A, there is no problem even if the removed layerreaches the interlayer below the recording layer.

Next, referring to FIG. 6G in one approach, the protective film and theresist layer are removed, after which the protective film B 25 is formedsuch as via sputtering using a carbon film or chemically passive metal,or some other method, as shown in FIG. 6H. Next, as shown in FIG. 6I, inone approach, an organic material layer 19 a and an oxide layer and/orhydroxide layer 19 b may be formed in a film thickness direction of theregion where the carbon film or chemically passive metal in the concaveportions of the magnetic region of the recording layer has not beenfully formed, in one approach. In this case, the carbon film orchemically passive metal layer is partially formed in the film thicknessdirection, although this is not shown in the figure.

Next, as shown in FIG. 6J in one approach, the concave portions in thesurface of the unprocessed element may be filled with a nonmagneticmaterial 18 to a slightly greater depth than the thickness of theconcave portions, such as by using sputtering or some other method.Next, as shown in FIG. 6K, the excess filler layer 18 (nonmagneticregion) and protective film B 25 (the upper portion of the magneticregion of the recording layer) may be removed using etching, such aschemical-mechanical planarization (CMP), or some other method, and theconcave portions on the surface of the medium formed in the steps shownin FIGS. 6D-6J may be planarized.

Then, as shown in FIG. 6L in one approach, the protective layer A 20 maybe deposited using chemical vapor deposition (CVD) or some other methodon the planarized surface, after which a liquid lubrication layer 23 maybe coated on the protective film A 20, in one approach. As a result ofthe method shown in FIGS. 6A-6L, the recording medium shown in FIG. 5Amay be obtained.

For the corrosion resistance test, disks on which various kinds oflubricants were formed to around 1.0 nm were left to stand for 72 hoursunder high-temperature, high-humidity conditions of temperature of about65° C. and relative humidity of about 95% RH, after which 3 ml of amixed solution of 3% nitric acid and 3% hydrogen peroxide was dripped onthe surface of the disk, which was then left to stand for a further 1hour at room temperature (25° C.), after which the solution wascollected, and the cobalt (Co) concentration was measured usinginductively coupled plasma-mass spectrometry (ICP-MS). A Coconcentration of 10 μ/L was taken as A, 10-50 μ/L was taken as B, 50-100WL was taken as C, and 100 μ/L a was taken as D. A rank of B or abovemay be preferred in practice. Specific exemplary embodiments in whichthe approaches, systems, and methods described herein are applied arenow described with reference to the tables and figures.

In any embodiments, it is possible to obtain a magnetic recording devicehaving a recording density of 95 gigabits per square inch byconstructing a magnetic recording device using: a magnetic recordingmedium as described herein, a mechanism for driving the magneticrecording medium in the recording direction, a magnetic head providedwith a recording portion and a reproduction portion, and a signalprocessing mechanism for carrying out waveform processing of inputsignals and output signals with respect to the magnetic head.

In a first exemplary embodiment, the layer structure shown in FIG. 5Aand Table 1 was used. Carbon was used in the protective film B, and thefilm was formed to 2 nm. The filler used was SiO₂. A disk as shown inFIG. 5H was immersed for 30 minutes in an aqueous solution containing 1wt % benzotriazole and 10% of 30% H₂O₂, and a benzotriazole layer and anoxide layer and/or hydroxide layer were produced in the position of thevertical portions of the concave portions of the magnetic region of therecording layer, as shown in FIG. 6I. Also, the corrosion resistance andmedium signal-to-noise ratio (SNR) of this medium (sample 1-1) weretested, and it was possible to achieve high SNR of 18 dB or more, andexcellent corrosion resistance achieving rank A.

In a first comparative example, the layer structure shown in FIG. 5A andTable 1 was used. Carbon was used in the protective film B, and the filmwas formed to 2 nm. The filler used was SiO₂. A disk as shown in FIG. 5Hwas immersed for 30 minutes in a solution of 1 wt % benzotriazole, and abenzotriazole layer and an oxide layer and/or hydroxide layer wereproduced in the position of the vertical portions of the concaveportions of the magnetic region of the recording layer, as shown in FIG.6I. Also, the corrosion resistance and medium SNR of this medium (sample1-2) were investigated, and even though it was possible to achieve ahigh SNR of 18 dB or more, the corrosion resistance achieved rank Cwhich was far worse than in the case of sample 1-1.

In a second exemplary embodiment, a sample with a different type ofheterocyclic compound for forming the organic material layer formed inthe position of the vertical portions of the concave portions of themagnetic region of the recording layer was then produced, and theresults of evaluating the medium SNR and corrosion resistance in thesame way as in sample 1-1 are shown in Table 2. The concentration of theheterocyclic compound in the aqueous solution in which the medium wasimmersed was 1.0 wt %, and, where there was not complete dissolution,the compound was first of all dissolved in an organic solvent such asethanol, after which it was mixed with the aqueous solution. 2-10 is anexemplary embodiment which does not employ a heterocyclic compound, butmakes effective use of a compound having unpaired electrons. 10% of 30%hydrogen peroxide oxidant was added to all of the solutions.

TABLE 2 Heterocyclic Compound for Forming the Organic Layer in theCorrosion-Resistance Corrosion- Sample Magnetic Region/Filler RegionRank Resistance Rank 2-1 no treatment D 2-2 benzotriazole A 2-31,2,3-triazole A 2-4 nitro-1H-benzotriazole A 2-5 methyl-benzotriazole A2-6 carboxy benzotriazole A 2-7 uric acid A 2-8 pterin A 2-9phenyl-1,3,4-thiadiazole-2-triol A 2-10 mercaptobenzothiazole A 2-11ethylenediamine A

All of the samples exhibited excellent corrosion resistance.Furthermore, the SNR was also good at 18 dB or more. It is clear thatthe metals had excellent adhesion with the CoCrPt—SiO₂ used for therecording layer, because of the excellent corrosion resistance.

In a third exemplary embodiment, the method involved splitting the stepof forming the oxide and/or hydroxide and the step of forming theorganic material layer, in the step for forming the oxide layer and/orhydroxide layer and the organic material layer on the disk in the stateshown in FIG. 5H. That is to say, a disk in the state shown in FIG. 5Hwas exposed for 2 hour to an atmosphere at 120° C. in order to form theoxide and/or hydroxide on the magnetic layer. After this, the disk wasimmersed for 30 minutes in an aqueous solution containing 1 wt %benzotriazole, and a benzotriazole layer and an oxide layer and/orhydroxide layer were produced in the position of the vertical portionsof the concave portions of the magnetic region of the recording layer,as shown in FIG. 5I. The subsequent steps were the same as in the firstexemplary embodiment. When the corrosion resistance and medium SNR ofthis medium (sample 3-1) were investigated, it was possible to achievehigh a SNR of 18 dB or more, and excellent corrosion resistanceachieving rank A.

In a fourth exemplary embodiment, a sample was produced using materialsother than hydrogen peroxide as the oxidant used in the first exemplaryembodiment, and the results of evaluating the medium SNR and corrosionresistance in the same way as in the first exemplary embodiment areshown in Table 3. All of the samples exhibited excellent corrosionresistance. Furthermore, the SNR was also good at 18 dB or more. It isclear that the metals had excellent adhesion with the CoCrPt—SiO₂ usedfor the recording layer, because of the excellent corrosion resistance.

TABLE 3 Corrosion- Sample Oxidant Concentration Resistance Rank 4-1sodium perchlorate  1.0 wt % A 4-2 sodium perchlorate 0.02 wt % A 4-3ceric ammonium nitrate 0.005 wt %  A 4-4 sodium chlorate 0.05 wt % A

In a fifth exemplary embodiment, the corrosion resistance was evaluatedafter using a chemically passive metal instead of the carbon which wasused for the protective film B employed in the first exemplaryembodiment. In all cases, when the medium SNR and corrosion resistancein FIG. 5L were ultimately investigated, it was possible to achieve highSNR of 18 dB or more, and excellent corrosion resistance of rank A.

TABLE 4 Material of Protective Film B Corrosion- Sample (ChemicallyPassive Metal) Resistance Rank 5-1 Ta₇₀Cr₃₀ A 5-2 Cr₇₀Nb₃₀ A 5-3Cr₅₀Zr₅₀ A 5-4 Cr₅₀Ti₄₅Nb₅ A 5-5 Cr₅₀Ti₅₀ A

In a sixth exemplary embodiment, the procedure shown in FIGS. 8A-8K isdifferent than the production method shown in FIGS. 6A-6L. The stepsshown in FIGS. 8A-8F are similar to the steps shown in FIGS. 6A-6F. Inthe step shown in FIG. 8G, the protective film C was left, rather thanbeing removed as far as the protective film C in the step in FIG. 6G. Inthis state, the organic material layer and the oxide layer and/orhydroxide layer were formed as in FIG. 8H. The subsequent steps aresimilar as to those shown in FIGS. 6I-6L. When the sample was producedusing this step, there was a difference between when the carbon orchemically passive metal layer was, or was not, present in the bottomparts of the concave portions of the magnetic region in the recordinglayer, as is clear from comparing FIG. 8K and FIG. 6L. Acorrosion-resistance rank of B was obtained for the sample in FIG. 8Kproduced by the above method. The corrosion resistance was slightlyworse than when the carbon layer was present in the bottom parts of theconcave portions in exemplary embodiment. This is believed to be becausedefects are produced by the damage caused by processing of the concaveportions of the recording layer, and paths are partially formed with theRu of the underlying interlayer.

In a seventh exemplary embodiment, as shown in FIG. 7A, in a step forforming the unevenness in the magnetic region of the recording layer,the recording layer at the bottom portions of the concave portions wascompletely removed, and the interlayer was exposed, after whichproduction was carried out in the following order: formation of theprotective film B, formation of the organic material layer and the oxideand/or hydroxide layer, formation of the filler layer, removal of thefiller layer and protective film B (upper surface) (CMP), formation ofthe protective film A, and possible application of lubricant (as shownin FIG. 7B, sample 7-1). The material of the recording layer and filmthickness were similar as to in sample 1-1. When the corrosionresistance and medium SNR of this medium (sample 7-1) were investigated,it was possible to achieve high SNR of 18 dB or more, and excellentcorrosion resistance of rank A.

In an eighth exemplary embodiment, when the sample was produced underthe conditions of exemplary embodiment 1, the results were obtained frominvestigating the change in corrosion resistance when the time for whichthe sample was immersed in 10 wt % benzotriazole and 10% of a 30% H₂O₂solution was varied, and the thickness of the oxide and/or hydroxidelayer was varied. When the thickness of the oxide and/or hydroxide layerwas 1.0 nm or greater, a rank of B or greater was obtained and thecorrosion resistance improved.

TABLE 5 Treatment Thickness of Oxide and/ Corrosion- Sample Time (min)or Hydroxide Layer (nm) Resistance Rank 8-1 0 0.5 D 8-2 1 0.8 C 8-3 51.0 B 8-4 10 1.2 A 8-5 30 1.5 A

FIG. 9 schematically shows a magnetic recording device in which varioustypes of media described in embodiments described herein may be applied.Furthermore, FIG. 10 is a cross-sectional view along line A-A′ in FIG.9. This device has a structure in which the following are providedinside an enclosure: the patterned medium described in embodimentsherein; a drive mechanism for rotating the medium; a magnetic headcomprising a recording part/reproduction part; a drive mechanism foroperating the magnetic head relative to the patterned medium; and arecording and production mechanism for reproducing input signals fromthe magnetic head and output signals from the magnetic head. Themagnetic head may be a composite head comprising a trailing shieldhead-type recording head, and a reproduction head employing ashield-type MR reproduction element (GMR film, TMR film, etc.). Themagnetic recording device is equipped with a magnetic recording mediumhaving excellent corrosion resistance and a magnetic head having a steepfield gradient, and as a result it is possible to achieve excellentcorrosion resistance.

In another exemplary embodiment, a surfactant was added to thecomposition described in exemplary embodiment 1. The surfactants usedwere: dodecyl sulfate, stearic acid, toluenesulfonate, cetyltrimethylammonium salt, tetramethylammonium hydroxide, lauryl betaine,polyethylene glycol, and polyvinyl alcohol. The concentration was 1 g/L.The treatment time was 5 minutes. When a surfactant was added, thecorrosion-resistance rank was A (compared to B without the additionthereof), so corrosion resistance was improved by adding a surfactant.

In another comparative example, the protective film B was carbon and anevaluation was carried out without the provision of an organic materiallayer (sample 2-1). The results showed a corrosion-resistance rank of Dand extremely poor corrosion resistance.

According to another comparative example, another surface treatmentmethod was used instead of using a heterocyclic compound to form theorganic layer in the magnetic region/filler region shown in FIG. 5A. Thebasic composition and film thickness were otherwise the same as in thefirst exemplary embodiment. The recording layer was lost in each caseand it was not possible to produce a disk as shown in Table 6.

TABLE 6 Surface Treatment of Magnetic Region Corrosion- Sample ofRecording Layer Resistance Rank 8-1 Chromic Acid (Chromate Treatment)N.G. 8-2 Chromium Chloride (Trivalent Chromate) N.G. 8-3 ZirconiumPhosphate Treatment N.G. 8-4 Zinc Phosphate Treatment N.G.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Thus, the breadth and scope of an embodiment of the presentinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

What is claimed is:
 1. A method for producing a magnetic recordingmedium, the method comprising: forming a magnetic material layer above asubstrate; transferring an uneven pattern to the magnetic material layerto form concave portions and convex portions, the convex portions beingmagnetic regions; depositing a nonmagnetic material above the concaveportions to form nonmagnetic regions; forming an oxide layer and/orhydroxide layer above the magnetic regions of the recording layer; andforming an organic material layer which exhibits a corrosion-inhibitingcharacteristic with respect to cobalt or cobalt alloy above the oxidelayer and/or hydroxide layer.
 2. The method as recited in claim 1,wherein the organic material layer and/or the oxide layer and/orhydroxide layer are formed by immersing the magnetic material layer in,or spraying the magnetic material layer with, a liquid comprising thecorrosion-inhibiting organic material, an oxidant and a surfactant, oran organic material and an oxidant.
 3. The method as recited in claim 2,wherein the oxidant comprises at least one of: hydrogen peroxide,chloric acid, perchloric acid, persulfuric acid, nitric acid and saltsthereof, and ceric ammonium nitrate.
 4. The method as recited in claim1, wherein the organic material layer and/or the oxide layer and/orhydroxide layer are formed in the presence of ultrasonic waves.
 5. Themethod as recited in claim 1, wherein the corrosion-inhibiting organicmaterial comprises a heterocyclic compound having nitrogen groups. 6.The method as recited in claim 5, wherein the heterocyclic compoundhaving nitrogen groups comprises at least one of: benzotriazole;1,2,3-triazole; 1,2,3,4-tetrazole; 3-amino-1,2,4-triazole;nitro-1H-benzotriazole; carboxy benzotriazole; 5-methyl-benzotriazole;and uric acid.
 7. The method as recited in claim 1, wherein thesurfactant comprises at least one of: an anionic surfactant, a cationicsurfactant, an amphoteric surfactant, and a non-ionic surfactant.
 8. Themethod as recited in claim 7, wherein the anionic surfactant comprisesat least one of: dodecyl sulfate, stearic acid, and toluenesulfonate,wherein the cationic surfactant comprises at least one of:cetyltrimethyl ammonium salt and tetramethylammonium hydroxide, whereinthe amphoteric surfactant comprises lauryl betaine, and wherein thenon-ionic surfactant comprises at least one of: polyethylene glycol andpolyvinyl alcohol.